Pulp-bleaching apparatus



March 24, 1925.

J. E. HEISKANEN PULP B LEACHING APPARATUS Filed April 27, 1922.

v and l'clear specification.

Patented Mar. 24, 1925.

i' UNITEDSTATES PATENT OFFICE.

.IAIMAE E. HEIsxANEN, or ENso', FINLAND, As'sIGNon rro srEBBINs ENGINEERING AND MANUFACTURING COMPANY, E wATERroWN, NEW Yoan, A conronArIoN or NEW Yonx.

PULP-BLEACHING APPARATUS.

' "Application filedv April 27, 1922. Serial No.l556,894.

To 'all whom t may concern:

Be i known that I, JALMAR E; IIEIS- KANEN, a citizen of Finland, and a resident i of Enso, Finland, have invented certain new and useful Improve ents in Pulp-Bleaching` Apparatus, of whici [the following is a full This invention is designed to provide a simple and eiicient apparatus especially tho not exclusively for carrying out the pulp-bleaching method disclosed in my Pat-l ent No. 1,277 ,926, dated Sept. 3, 1918, and

- the special object of the invention is to so construct the apparatus as to reduce to a minimum the consumption of steam, bleach and power, as more fully 'hereinafter seti forth.

In the drawingp Fig. 1 is a vertical sectional view of one of the units ofmyfimproved apparatus;

Fig. 2 is a plan view ofl several of the units connected together by1 screw-conveyor devices.

Referring to the drawing annexed,'5 is a main cylindrical tank in which is supported concentrically, by means of suitable Ysu ports 6, av supplementaltank or uptake p, the lower, inlet end of this uptake being supported at a distance above the bottom as in my former Patent 1,277 ,926. `In the preferred operation, the screw-impeller pulls thev pulp downwardly in the main tankv and-v The operation of this apparatus is the same clrculated insaid unit; and so on tothe last -unit ofthaplant, from which last unitthe bleachedfpulp is discharged in any suitabler manner. I

An advantage in the present screw-conve-yer arrangement over my former patent is thatthe thrust in the present apparatus is downwardly, thus tending to hold4 the shaft in its stepped bearing, whereas inthe apparatus covered by my former patent the thrust constantly tended to unstep the shaft.

- It will beunderstood that the screw-con-v of the main tank while the upper en'd of this central tank terminates at a point below the top of the main tank. Arranged in the.7 v lower part of the main tank`is a vertical screw-conveyor 8 whichextends across the space between the lower end of the. central tank and the bottom of the main tank vand extends up a suitable distance into the suppilemental ztank. The screw-conveyor approximately fits the interior of the-lower end of the central uptake butrat a point above the screw-conveyor the interior diameter of the central'uptake increases.

The shaft 9 of the lscrew-conveyor extends downwardly through a stuling-boxA in the lower end of the .main tank land is stepped in a suitable step-bearing 10 below.

' Connecting each pair of adjacent main tanks is a trough 11 whose bottom is just above the upper end of the central, uptake tank.v

' thickness of stock being wor veyor 8 may be `extended nip into the uptake to `any distance desired, epending on the ed. With thisv apparatus, I am enabled to work much heavier stock than with my former apparatus.- My present apparatus is further desirable on the` ground that it isysimpler and more compact and ensures a more thorough,

even treatment of the stock.

. The purpose ink enlarging the internal y diameter of the uptake at a point above the narrowed throat-like entrance thereof is to provide for expansion of the stock after it. passes) tlie narrowed throat, tothus permit the stock to be pushed upwardly in the up- Y take with decreased friction. It will be ob` In each trough is arranged a screw-con-lv veyor 12, these conveyors being all aiiixed to a common shaft 13 so that they shall be smultaifeously rotated at a uniform speed.

served that the bottom of the main tankis rounded Ito thus insure a substantially uniform delivery of the stock from all direc-. tions to the pro eller and thus also insure against any dea spaces in the, tank. The elimination of dead spaces in the bottom of the main tank avoids the necessity of .em-

ploying a special form of agitator' or gatherer to bring the stock to the propeller.

As hereinbefore stated, myinvention is v designed especially to handle' paper stock of heavy density, as heretofore it has been impossible to bleach high percentage stock with the apparatus known, except possibly by veryv costly methods. One of the diculties lies n keeping the -heavy stock in uniform circulation, as othervse an effectual and ecient bleaching action cannot be maintained. ln my present invention, ll can maintain a constant uniform circulation of heavy stock and in 'an apparatus that is exceedingly compact and inexpen- Asiveas compared with previous plants for over the upper edge of the uptake-tank takes place all around the same being naturally distributed equally around the rim of the uptake-tank. lfn this way and by reason of the fact that the outer main tank is circular in cross-section, as near uniform movement of the stock as is ossible is maintained..` This is promote by having the lower end of the main tank. wall rounded,

`so as to merge into the bottom wall of the tank, thereby delivering the gravitating stock directly to the propeller screw, the delivery being even all around and being accomplished without the necessity o-f employing stirrers or gatherers in the bottom of the main tank. v V

To make the foregoing apparatus effective and economical, it is essential that the 'two tanks be vertically arranged and that ,they be of considerable height in order to get the capacity needed for economical operation. The diliculty in employing a high uptake-tank is that in pushing the heavy stock up through the same, a considerable friction is generated as this stock is semisolid and approximately the consistency of wet sand. To move thls stock steadily and slowly upwardlyin the uptake requires the expenditure of considerable power. Now,

in order to reduce this power to an economical point, l provide for easing up the upward flow of thestock. To do this, I enlarge the uptake at a point beginning just above the screw and extending the full height of the' uptake, in order that, as

.heretofore stated, the compression of the lstock as it is forced through the throat of the uptake by the impeller may relieve itself as soon as it has passed the impeller. As soon as the stock passes the impeller, it

loosens and ex ands. and thus greatly reduces the friction a ainst the wall of the uptake. It is desira le that the enlarging t of the uptake shall be only slightly greater than the diameter of the screw and also that thefenlarged part of the uptake shall be of the same diameter throughout, in order aaeonea the upward movement of the pulp shall be practically" uniform throughout the crosssection of the uptake.

li do not desi-re to be understood as limiting myself to the precise details of construction and arrangement shown, as variations and modifications therefrom 'may be made without departing from the spirit and scope of my invention and improve'- Ine-Its. I therefore reserve the`right to all such variations and modifications as prop-l erly fall within the scopel of my invention and improvements and as set forth in the terms of the following claims.

What l claim is:

l. ln an apparatus for bleaching pulp, a main tank, a central cylindrical tank arranged within the main tank and having its lower open end terminating above the bottom of the main tank, and a shaft carrying a screw impeller extending across the space between the two ends of the tanks and up into the central tank, the interior diameter of the lower end of the central tank being approximately the same as the diameter of the screw impeller while the upper part of the central tank has an increased internal diameter.

2. ln an apparatus for bleaching pulp, a main tank circularv .in cross-section, anI inner uptake-tank circular in cross-section arranged centrally within said main tank and having awlower unobstructed open end and also an upper unobstructed open end, the lower. end of the uptake-tank terminatingy above the bottom of the main tank and its upper end terminating below the top of the main tank, an impeller-screwF extending across the space between the lower end of the uptake-tank and the bottom ofthe main tank and into the uptake-tank, the interior diameter of the lower end of the central up.- take-tank being approximately the same as the diameter of the screw-impeller, while the part of the central uptake-tank above the screw-impellerhas an increased internal diameter uniform to the top of the uptake-tank.

3. In an apparatus for bleaching pulp, a main tank circular in cross-section, an 1nner uptake-tank circular in cross-section arranged centrally within said main tank and having a lower unobstructed open end and also an upper unobstructed open end, the lower end of the uptake-tank terminating above the bottom ofthe main tank and its upper end terminating below the top of the main tank, an impeller-screw extending across the space between the lower end of the uptake-tank and the bottom of the main tank and into the uptake-tank, the interior diameter of the lower end of the central uptake-tank being approximately the' same as t the diameter of the screw-impeller, while the part of the central uptake-tank vabove the screw-impeller has an increased internal In testimony whereof I hereunto aix my diameter uniform to the top of the uptakesignature. A

tank, the wall of the main tank being rounded al1 around to merge into the bot- JALMAR E. HEISKANEN.

5 tom Wall of the main yank, to thereby insure Witnesses:

delivery of the stock to the impeller Without ERNEST W. LINDQmsT the use of a. gathering appliance. FRANS E. TELILENIUS. 

